Piezoelectric devices are presently being employed in greater numbers of applications and in a wide ranging area of technologies. Piezoelectric devices make use of one or more piezoelectric ceramic wafers that are adapted to bow or deform in response to an electric current applied to the wafer. Such piezoelectric wafers also produce an electrical output when they are flexed or deformed from an initial, non-flexed configuration. Thus, piezoelectric wafers are especially useful in applications involving actuators and vibration energy harvesting apparatuses. The following U.S. patents and applications involve various implementations of piezoelectric materials, and are each hereby incorporated by reference into the present application: U.S. Pat. No. 6,858,970 and U.S. Ser. No. 10/909,784, filed Jul. 30, 2004.
Another device which has only recently achieved practicality is a Stirling engine. Stirling engines have existed in various forms for many years, however, it has been recent breakthroughs in the design of engine chamber seals that has made these devices practical. A Stirling engine utilizes temperature gradients to convert thermal energy into mechanical energy. Typically, the Stirling engine includes one or more pistons that are driven in a reciprocating fashion by converting thermal energy into mechanical energy. Recently, Stirling engines have shown promise as a low cost, high efficiency solar powered generator for U.S. power grid and spacecraft electric power generation systems. The ability of the Stirling engine to meet or exceed the performance of concentrated photovoltaics has been recently recognized by engineers and researchers interested in exploring alternative power generation systems for use in spacecraft.
One drawback with a typical Stirling engine is that the mechanical energy is typically converted to electrical energy using a very large AC electromagnetic generator. A large electromagnetic generator, however, can be a serious drawback for spacecraft applications, where weight is an important consideration.
Thus, it would be highly desirable to provide some means for generating electric power from a mechanical input device, for example, from one or more pistons of a Stirling engine. It would further be highly desirable if such a device formed a small, lightweight, and highly efficient apparatus for converting mechanical energy to electrical power. Such a device would significantly enhance the utility of other components, such as Stirling engines. Such a device could enable a Stirling engine to be used in various power generating applications which, at the present time, are not feasible because of the size and weight of typical electromagnetic generators presently employed for use with Stirling engines in power generating applications.